1. Field of Art
This application relates to a yttria sintered body, an electrostatic chuck using a yttria sintered body, and a manufacturing method of a yttria sintered body.
2. Description of Related Art
Conventional semiconductor manufacturing apparatus, liquid crystal manufacturing apparatus, and the like employ an electrostatic chuck for chucking a semiconductor substrate, liquid crystal substrate, and the like to be held. The electrostatic chuck is made by aluminum nitride, alumina, or the like that is excellent in heat resistance, corrosion resistance, etc.
The yttria sintered body has a very high corrosion resistance, and has applications under study, to corrosion-resistive materials to be used in a corrosive gas environment, as disclosed in Japanese Patent Application Laid-Open Publication Nos. 2002-68838 and 2002-255647.
Recent electrostatic chucks are subject to more severe criteria of corrosion resistance than ever. For example, electrostatic chucks are exposed to a plasma environment of more severe halogen corrosive gas in their etching processes to which an in-situ cleaning is introduced, so that corrosion may be unsuccessfully prevented even on electrostatic chucks made by aluminum nitride, alumina, or the like.
Then, a trial was made of application of a highly corrosion-resistant yttria sintered body to an electrostatic chuck, with an encountered new problem. The yttria sintered body is inferior in some mechanical properties, such as flexural strength and fracture toughness. As the yttria sintered body constitutes the electrostatic chuck, inferiority in some mechanical properties may cause damages in processes of the manufacturing, with a reduced yield. For example, cracks or chipping may occur when drilling a hole for insertion of a terminal to be joined to an electrode, or cracks may develop with thermal stresses when brazing a terminal to an electrode.
Besides, for an electrostatic chuck to exhibit a high chucking performance, it is essential for its dielectric layer to have an adequate volume resistivity. However, the volume resistivity of conventional yttria sintered bodies reside in an unfavorable range for the electrostatic chuck to be adapted to make use a Johnsen-Rahbek force, thus failing to provide a high chucking performance.
It therefore is an object the invention to provide a yttria sintered body having an excellent corrosion resistance and mechanical strength, and a controlled volume resistivity. It also is an object of the invention to provide an electrostatic chuck having an excellent corrosion resistance and mechanical strength, and a high chucking performance.